Sand control screen having a micro-perforated filtration layer

ABSTRACT

A sand control screen ( 40 ) includes a perforated base pipe ( 42 ) and a filter layer ( 50 ) that has micro-perforations ( 52 ) therein. The filter layer ( 50 ) is attached to the base pipe ( 42 ) along the entire length of the filter layer ( 50 ). Channels ( 46 ) are formed between the base pipe ( 42 ) and the filter layer ( 50 ) to allow fluid to flow therebetween. The sand control screen ( 40 ) is formed by micro-perforating a length of material, such as sheet metal, to form the filter layer ( 50 ), creating channels ( 46 ) that will allow fluids to flow between the base pipe ( 42 ) and filter layer ( 50 ), wrapping the filter layer ( 50 ) around the base pipe ( 42 ), attaching the filter layer ( 50 ) to the base pipe ( 42 ) along the length of the filter layer ( 50 ) and creating a seam between the two edges of the filter layer ( 50 ).

TECHNICAL FIELD OF THE INVENTION

This invention relates, in general, to a sand control device used duringthe production of oil, gas or water and a manufacturing process relatedto the same and, in particular, to a sand control screen having amicro-perforated filtration layer.

BACKGROUND OF THE INVENTION

Without limiting the scope of the present invention, its background willbe described with reference to producing fluid from a subterraneanformation, as an example.

After drilling each of the sections of a subterranean wellbore,individual lengths of relatively large diameter metal tubulars aretypically secured together to form a casing string that is positionedwithin each section of the wellbore and cemented in place. This casingstring is used to increase the integrity of the wellbore by preventingthe wall of the hole from collapsing and to prevent movement of fluidsfrom one formation to another formation.

Once the process of drilling and installing casing is finished, thecompletion process may begin. The completion process comprises numeroussteps including the creation of hydraulic openings or perforationsthrough the casing string, the cement and a short distance into thedesired formation or formations so that production fluids may enter theinterior of the wellbore. In addition, the completion process mayinvolve formation stimulation to enhance production, installation ofsand control devices to prevent sand production and the like. Thecompletion process also includes installing a production tubing stringwithin the well casing. Unlike the casing string that forms a part ofthe wellbore itself, the production tubing string is used to produce thewell by providing the conduit for formation fluids to travel from theformation depth to the surface.

Typically, the production tubing string extends from the surface to theformations traversed by the well and includes one or more productionpackers. The purpose of the packers is to support the production tubingand other completion equipment, such as one or more sand control screensthat may be placed adjacent to the producing formations, and to seal theannulus between the outside of the production tubing and the inside ofthe well casing to block movement of fluids through the annulus past thepacker locations. Accordingly, once the production tubing string,including the production packers and sand control screens are in place,all production from the formation that enters the production tubing mustpass through a sand control screen.

One purpose of the sand control screens is to prevent the movement ofunconsolidated formation particles such as sand into the productiontubing. Such particle movement commonly occurs during production fromcompletions in loose sandstone or following hydraulic fracture of aformation. Production of these materials causes numerous problems in theoperation of oil, gas or water wells. These problems include plugging offormations, tubing and flow lines, as well as erosion of tubing,downhole equipment and surface equipment. These problems lead to poorproductivity, high maintenance costs and unacceptable well downtime.

Existing screens typically use a wire wrap filter media or a wire meshfilter media attached to a base pipe to achieve sand control. Wire wrapsand screens may comprise a continuous single wire wrapped around thebase pipe. More recent versions use a jacket that is fully formed from asingle wire prior to attachment to the base pipe, with vertical ribsproviding a stand-off from the base pipe. Variations in the gauge ofwire and corresponding variations in the spacing between wraps of thewire provide sand screens for different conditions. Wire mesh sandscreens use one or more woven metal layers to trap particulate matter.As with wire wrap screens, wire mesh sand screens are available in anumber of gauges having openings of various sizes.

In addition, some screen designs use prepacked sand confined around theperforated base pipe. These prepacked screens are constructed byfabricating the metal components, then forcing pack sand, either resincoated or uncoated, between the perforated base pipe and an inner wirescreen or between an inner wire screen and an outer wire screen of amulti-layer screen. Alternatively or additionally, a gravel pack may beplaced in the production interval surrounding the installed sand controlscreens.

It has been found, however, that existing sand screens continue to havea number of drawbacks. For example, variations in the gauge of the wireor improper manufacture can result in inconsistencies in the openingsize. Larger gauges of wire become increasingly difficult to bend, whilesmaller gauges are more easily damaged in the processes of manufactureand installation or during production. Additionally, screens that usemultiple filter layers are, by their nature, difficult or impossible toclean. Still further, the attachment of the wire wrap screen or wiremesh screen to the base pipe is an ongoing cause of concern. The sandscreen filters are typically attached to the base pipe with conventionalwelding at both ends of the filter layer. A failure of any portion ofthe weld results in an uncontrolled opening and a loss of sand control.Therefore, a need has arisen for a sand screen that provides the desiredsand control function, is robust, easy to clean and simple tomanufacture.

SUMMARY OF THE INVENTION

The present invention disclosed herein comprises a sand control screenhaving a micro-perforated filter layer for filtering particles out offluid produced from a wellbore and a method for manufacturing the same.The sand screen of the present invention allows for precise, reliablyreproducible and infinitely variable opening size, shape, density andpattern in the micro-perforated filter layer, thereby providing thedesired sand control function. In addition, the sand control screen ofthe present invention is robust, easy to clean and simple tomanufacture.

The sand control screen having a micro-perforated filter layer of thepresent invention includes a base pipe having a plurality of openingsthat allow fluid flow therethrough and a filter layer having a pluralityof micro-perforations. The filter layer wraps around the base pipe andis attached thereto. A drainage layer such as channels, wire wrap orwire mesh between the base pipe and filter layer allows production fluidto flow between the filter layer and the base pipe.

In one embodiment of the sand control screen having a micro-perforatedfilter layer, the filter layer is made of sheet metal that is wrappedaround the base pipe. The sheet metal may be flat or corrugated. In theflat sheet metal embodiments of the sand control screen, channels may beformed in the outside surface of the base pipe or on the inside surfaceof the filter layer. In the corrugated sheet metal embodiments of thesand control screen, the corrugations form the channels between thefilter layer and the base pipe.

The filter layer may be attached to the base pipe using a variety oftechniques including fusion bonding, a friction fit, adhesives or thelike. Alternatively or additionally, the filter layer may be attached tothe base pipe using connectors, such as end caps, that seal the ends ofthe filter layer to the base pipe. The end caps may be attached to thebase pipe using welded, threading or similar techniques.

In some embodiments of the sand control screen, the filter layer has athickness between about 1/32nd inch and about ¼th inch. In otherembodiments, the opening shape of the micro-perforations at the surfaceof the filter layer can be a circle, an ellipse, a slot or other similarshape having a radius. Alternatively, the opening shape of themicro-perforations at the surface of the filter layer may have sharpedges such as squares, rectangles, triangles or other multi sidedpolygon or shape. In certain embodiments, the micro-perforations mayhave a tapering cross-section through the filter layer wherein thesmaller opening of this tapering cross-section may be oriented to eitherthe exterior or the interior of the filter layer.

In one embodiment of the sand control screen having a micro-perforatedfilter layer, the opening size of the micro-perforations has a maximumwidth of 500 microns. In other embodiments, the maximum width of themicro-perforations is between about 50 microns and 500 microns. Inanother embodiment of the sand control screen having a micro-perforatedfilter layer, the opening density of the micro-perforations is betweenabout 100 and 200 openings per square inch. In other embodiments, theopening density of the micro-perforations may be less than 100 openingsper inch or more than 200 openings per inch.

In one embodiment of the sand control screen having a micro-perforatedfilter layer, the opening pattern of the micro-perforations has auniform distribution. In other embodiments, the opening pattern mayinclude a nonuniform or selected distribution. For example, in thecorrugated sheet metal embodiment, the micro-perforations can be placedat the peaks and valleys of the corrugations, in the sides of thecorrugations or in any other arrangement that is desired. The size,shape, density and pattern of the micro-perforations are determined bythe desired flow area, the desired filtration capacity, the constituentsbeing separated from one another and the like.

In another aspect, the present invention is directed to a method ofmaking a sand control screen that includes fabricating a plurality ofopenings in the wall of a base pipe and creating a plurality ofmicro-perforations in a length of sheet metal having a first and asecond edge opposite each other to form a filtration media. The methodfurther includes forming a plurality of channels that allow fluid flowbetween the filter layer and the base pipe, shaping the filter layer tofit around the base pipe, bringing the first edge and the second edge ofthe filter layer substantially adjacent each other, attaching the filterlayer to the outer surface of the base pipe and coupling the first edgeof the filter layer to the second edge.

In some embodiments, the step of creating a plurality ofmicro-perforations in a length of sheet metal may be accomplished usinga water jet, a laser or similar technique. In certain installations, thesteps of shaping the filter layer to fit around the base pipe, bringingthe first edge and the second edge of the filter layer substantiallyadjacent each other, attaching the filter layer to the outer surface ofthe base pipe and coupling the first edge of the filter layer to thesecond edge may be performed at the location where the sand screen willbe used.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages of thepresent invention, references now made to the detailed description ofthe invention along with the accompanying figures in which correspondingnumerals in the different figures refer to corresponding parts and inwhich:

FIG. 1 is a schematic illustration of an offshore oil and gas platformoperating a sand control screen having a micro-perforated filter layerof the present invention;

FIG. 2 is a side elevation, partially cut away, of an embodiment of asand control screen having a micro-perforated filter layer of thepresent invention;

FIGS. 3A and 3B each show a section of the base pipe from an embodimentof a sand control screen having a micro-perforated filter layer of thepresent invention, enlarged to display knurling on the surface;

FIG. 4 is a cross-section through one wall of the embodiment of FIG. 2;

FIG. 5A is a side elevation of an embodiment of a sand control screenhaving a micro-perforated filter layer of the present invention;

FIG. 5B is a cross-section through a portion of the sand control screenhaving a micro-perforated filter layer shown in FIG. 5A;

FIG. 6 is a side elevation of an embodiment of a sand control screenhaving a micro-perforated filter layer of the present invention;

FIGS. 7A and 7B respectively display a cross-section through acorrugated filter layer of a sand control screen having amicro-perforated filter layer and an associated pattern ofmicro-perforations in the filter layer;

FIGS. 8A and 8B respectively display a cross-section through acorrugated filter layer of a sand control screen having amicro-perforated filter layer and an associated pattern ofmicro-perforations in the filter layer;

FIGS. 9A and 9B respectively display a cross-section through acorrugated filter layer of a sand control screen having amicro-perforated filter layer and an associated pattern ofmicro-perforations in the filter layer;

FIGS. 10A and 10B display possible orientations of themicro-perforations in the filter layer of a sand control screen having amicro-perforated filter layer of the present invention; and

FIG. 11 is a flowchart showing the manufacture of the sand controlscreen having a micro-perforated filter layer of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts whichcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention, and do not delimit the scope of theinvention.

Referring now to FIG. 1, a sand control screen having a micro-perforatedfiltration layer in use with an offshore oil and gas production platformis schematically illustrated and generally designated 10. Asemi-submersible platform 12 is centered over a submerged oil and gasformation 14 located below sea floor 16. Wellhead 18 is located on deck20 of platform 12. Well 22 extends through the sea 24 and penetrates thevarious earth strata including formation 14 to form wellbore 26.Disposed within wellbore 26 is casing 28. Disposed within casing 28 andextending from wellhead 18 is production tubing 30. A pair of sealassemblies 32, 34 provide a seal between tubing 30 and casing 28 toprevent the flow of production fluids therebetween. During production,formation fluids enter wellbore 26 through perforations of casing 28 andtravel into tubing 30 to wellhead 18. As part of the final bottom holeassembly, a sand control screen 38 having a micro-perforated filtrationlayer is included in tubing 30. Sand control screen 38 filters theparticles out of the formation fluids as the formation fluids areproduced.

Even though FIG. 1 depicts a cased vertical well, it should be noted byone skilled in the art that the sand control screen having amicro-perforated filtration layer of the present invention is equallywell-suited for use in uncased wells, deviated wells or horizontalwells. In fact, in certain well configurations, the sand control screenhaving a micro-perforated filtration layer of the present invention maybe used in conjunction with expandable tubing such that the tubing andthe sand control screen are expandable downhole after installation.Also, even through FIG. 1 depicts an offshore operation, it should benoted by one skilled in the art that the sand control screen having amicro-perforated filtration layer of the present invention is equallywell-suited for use in onshore operations. In addition, even though asingle sand control screen is depicted, it should be noted by oneskilled in the art that any number of sand control screens of thepresent invention may be coupled together to form one or more sandcontrol screen strings.

Referring to FIGS. 2-4, one embodiment of a sand control screen having amicro-perforated filtration layer is depicted and generally designated40. Sand control screen 40 includes a base pipe 42 that is depicted ashaving a plurality of openings 44 which allow the flow of productionfluids into the production tubing. One skilled in the art will recognizethat the number, size and shape of openings 44 are not critical to thepresent invention, so long as sufficient area is provided for fluidproduction and pipe integrity is maintained. For example, the base pipecould have a few as one opening. Alternatively, the base pipe could havea plurality of micro-perforations similar to those described below.Filter layer 50 is tightly attached to base pipe 42 and contains aplurality of micro-perforations 52. The size, shape, density and patternof the micro-perforations 52 are determined by the desired flow area,the desired filtration capacity, the constituents being separated fromone another and the like as well as the size of any packing sand used inassociation with an installation of sand control screen 40. In theillustrated embodiment, end caps 48 cover the ends of filter layer 50.In certain embodiments, however, these end caps 48 can optionally beomitted, as filter layer 50 may be tightly fused to base pipe 42.

The typical opening sizes in existing sand screens, e.g., 100-300microns, can be reproduced in the micro-perforated filter layer 50.Additionally, both larger and smaller opening sizes can be provided inthe disclosed micro-perforated filter layer 50 without the manufacturingdifficulties encountered when these sizes are manufactured in eitherwire wrap or wire mesh sand control screens. A wide variety ofintermediate size openings can also be easily produced. Micro-perforatedopening sizes for the disclosed micro-perforated filter layer can rangebetween 50 and 500 microns, providing opening sizes that are notcurrently available from any manufacturer.

Due to the manufacturing processes used to create filter layer 50, theshape of micro-perforations 52 is precisely controllable and reliablyreproducible. In the illustrated embodiment, micro-perforations 52 aredepicted as circular, however, micro-perforations 52 may also be formedin the shape of an ellipse, a slot or other similar shape having aradius. Alternatively, micro-perforations 52 may have sharp edges suchas squares, rectangles, triangles or other multi sided polygon or shape.

Due to the tight tolerances available in the manufacturing process usedto create filter layer 50, the density and pattern of micro-perforations52 are precisely controllable and reliably reproducible. For example,the opening density of micro-perforations 52 may be between about 100and 200 openings per square inch. Opening densities both less than 100openings per inch and more than 200 openings per inch are alsocontemplated by the present invention. The opening pattern ofmicro-perforations 52 can have a uniform distribution or a nonuniformdistribution. With the infinitely variable opening size, shape, densityand pattern in the micro-perforated filter layer available with thepresent invention, certain embodiments of the micro-perforated filterlayer not only allow for filtration of particles from production fluidsbut also allow for separation of fluid constituents from one another.For example, the micro-perforations may be configured to allow theproduction of hydrocarbon fluids therethrough but prevent the productionof water therethrough. Likewise, the micro-perforations may beconfigured to allow the production of liquid hydrocarbons therethroughbut prevent the production of hydrocarbon gases therethrough.

As best seen in FIGS. 3A, 3B and 4, the surface of base pipe 42 isknurled or machined to create channels 46 that form a drainage layerbetween base pipe 42 and filter layer 50 through which production fluidcan flow. FIG. 3A depicts a helical channel pattern wherein channels 46do not intersect. FIG. 3B depicts a helical channel pattern whereinchannels 46 intersect one another. In FIG. 4, channels 46 are depictedas notches in the outer surface of base pipe 42. Alternatively, thedrainage layer of sand control screen 40 could involve channels in theinner surface of filter layer 50. As another alternative, the drainagelayer of sand control screen 40 could involve the use of a wire mesh orwire wrap between base pipe 42 and filter layer 50.

Filter layer 50 is a surface-type filter, which removes particles thatare entrained in the production fluid at the surface of the filter.Because the particles remain on the surface, filter layer 50 isinherently easy to clean as particles can be washed away by a back-flowof fluid. This ability contrasts with depth filters, which trap theparticles within the filter and are inherently difficult or impossibleto clean.

Referring now to FIGS. 5A-5B, an alternate embodiment of a sand controlscreen having a micro-perforated filtration layer is depicted inelevation and in cross-section respectively and generally designated140. Sand control screen 140 includes a base pipe 142 that has aplurality of openings 144 which allow the flow of production fluids intothe production tubing. Filter layer 150 contains a plurality ofmicro-perforations 152. Filter layer 150 is corrugated prior toattachment to base pipe 142. end caps 148 prevent fluids from enteringbase pipe 142 without passing through filter layer 150 and provide anadditional means of attachment. The corrugations in filter layer 150form large channels 146 between filter layer 150 and base pipe 142through which production fluid flows to reach production tubing 30.

With reference now to FIG. 6, a further alternate embodiment of a sandcontrol screen having a micro-perforated filtration layer is depicted inelevation and generally designated 240. Sand control screen 240 includesbase pipe 242 with a plurality of openings (not shown) to allow the flowof production fluids into the production tubing. Filter layer 250contains micro-perforations 252. Filter layer 250, like filter layer 150of FIG. 5A, is corrugated prior to attachment to base pipe 242. However,the corrugations of filter layer 250 run circumferentially with respectto base pipe 242, rather than longitudinally, as in filter layer 150.End caps 248 protect and seal the ends of filter layer 250 to base pipe242. The corrugations in filter layer 250 form large channels betweenfilter layer 250 and base pipe 242 through which production fluid flowsto reach production tubing 30.

When the micro-perforated filter layer is corrugated, the placement ofthe micro-perforations can be varied as necessary or desirable toprevent long term plugging of the filter and to maintain the desiredflow area. With reference now to FIGS. 7A-9B, three embodiments ofmicro-perforations in a corrugated filter layer are displayed. In theseillustrations, only the filter layer, such as filter layer 150 of FIG.5, is shown. FIGS. 7A-7B contain filter layer 300 havingmicro-perforations 302 shaped to form slots. These slots 302 are createdonly in the peaks and valleys of the corrugations. In order to promotebridging of sand particles across slots 302, the width of the slots asmeasured across their narrowest surface dimension is sized according toconditions in the producing formation and the desired filteringcharacteristics. In an alternate embodiment, shown in FIGS. 8A-8B,filter layer 310 contains micro-perforations 312 that form ellipses atthe surface of the filter layer. The ellipses 312 are formed in thesides of the corrugations, but are eliminated from the peaks andvalleys. Removing the micro-perforations from the peaks may preventplugging while the sand control filter is installed. As in slots 302,the width of ellipses 312 as measured across their narrowest surfacedimension is sized as dictated by the producing formation and thedesired filtering characteristics. A further alternate embodiment isshown in FIGS. 9A-9B, which contain filter layer 320 havingmicro-perforations 322 that form circles at the surface of the filterlayer. In this example, circles 322 are formed only on the sides of thecorrugations, but not in the peaks or valleys. The diameter of thecircle at the surface of the filter is sized appropriately for theproducing formation and the desired filtering characteristics. One ofordinary skill in the art will understand that these arrangements areexemplary and do not limit the shape or distribution of themicro-perforations. In some embodiments, a shroud may be placed to theexterior of the corrugated filter layer to prevent damage duringinstallation, but this is not necessary to the operation of the sandcontrol screen.

The use of a corrugated filter layer with the sand control screen of thepresent invention provides certain advantages over the non-corrugatedembodiments. For example, the addition of corrugations to the filterlayer provides an increased flow area over the non-corrugated version.Additionally, the corrugated configuration reduces thermal effectsrelative to the bond between the filter layer and the base pipe.

With reference now to FIGS. 10A-10B, in at least some embodiments, themicro-perforations are formed using a water jet or laser cuttingprocess. When these methods are used, the micro-perforations may haveslightly tapering walls. For example, when the surface shape is acircle, the micro-perforation may have the shape of a truncated cone.Consequently, a slightly larger opening is found on one side of thefilter layer than on the other side. If we consider the top of thefigure to be the outside surface of the filter layer, FIG. 10A showsmicro-perforations 332 containing a larger opening to the outside offilter layer 330. FIG. 10B shows micro-perforations 342 containing asmaller opening to the outside of filter layer 340.

Referring now to FIG. 11, a method of making the sand screen of thepresent invention will now be discussed. In step 400, a section of basepipe is perforated to create openings. This step can be performed by thesame methods used to create openings for wire wrap and wire mesh typesand control screens. In step 402, a length of sheet metal ismicro-perforated using any available micro-perforation technique, suchas water jetting or laser cutting. The thickness of the sheet metal ispreferably in the range of 1/32nd inch to ¼th inch, and preferably3/16th inch thick. The configuration of the micro-perforations for agiven installation can be determined based upon formation condition andthe desired filtering characteristics. In situations in which thedesired sizes and/or shapes for the micro-perforations are not normallystocked, custom filter layers are feasible using the disclosed method.The specifications for the filter layer can be transmitted to amanufacturer of micro-perforated sheet metal for implementation. As willbe shown, once the filter layer is micro-perforated, the actual assemblyof the sand control screen is not technically difficult.

Micro-perforating results in more reliably shaped and sized openingsthan either wire wrapping or wire mesh screen methods, while tolerancesfor spacing of openings can be more easily controlled. Virtuallyinfinitely variable screen ratings can be provided by varying the size,shape, density and pattern of the micro-perforations. Very small micronratings can be produced by micro-perforation without loss of strength inthe filter material. Similarly, large micron ratings formed bymicro-perforation do not require the manipulations of large gauge wireand can be produced in sizes previously impossible to manufacture.

Once the sheet metal is micro-perforated to create the filter layer,channels are provided in step 404 to allow fluid flow between the filterlayer and the base pipe. For corrugated embodiments of themicro-perforated filter layer, the corrugations of the filter layer aredesigned to form channels between the filter layer and the base pipewhen the filter layer and base pipe are attached. For non-corrugatedembodiments, channels are formed in either the outer surface of the basepipe or in the surface that will be the interior surface of the filterlayer. In a preferred embodiment, the base pipe is placed in a knurlingmachine and knurls are created while the pipe is rotated, creating aspiral pattern of channels down the length of the base pipe that willlie under the filter layer. Cross-connections between adjacent channelscan also be formed to increase available cross-flow. FIGS. 3A-3B haveshown exemplary embodiments of knurling in the surface of the base pipe.In still another embodiment, the base pipe is treated to create anuneven, pebble-like surface. After the filter layer is attached to thebase pipe of this embodiment, the uneven surface creates interconnectedchannels between the base pipe and the filter layer.

The filter layer is shaped to fit around the base pipe in step 406 andthe filter layer and base pipe are attached to each other in step 408.In one embodiment, the filter layer is fusion bonded to the base pipe toform a direct metal-to-metal attachment. In fusion bonding, the filterlayer and the base pipe are placed in close contact with each other. Ahigh current is run through the adjacent filter layer and base pipe,causing the two pieces to fuse. With this technique, the filter layercan be attached to the base pipe along the entire length of the filterlayer, providing an extremely strong attachment. End caps, if necessaryor desired, can be added as part of this step. Once the filter layer isattached to the base pipe, the edges of the filter layer are sealed toeach other. In at least one embodiment, a seam weld is applied down thefull length of the filter layer, sealing the edges of the filter layertogether and forming a true one-piece, 360° filter.

In another embodiment of the attachment method, a friction fit is usedto join the filter layer to the base pipe. The filter layer is firstjoined to itself to create an open-ended cylindrical shape that is sizedto fit snugly over the base pipe. The cylindrical filter layer is thenheated to increase the diameter across the filter and slipped over thebase pipe. When sized properly, the cooled filter layer forms a tightfit to the base pipe.

One of ordinary skill in the art will realize that other methods ofattachment can also be used without deviating from the scope of theinvention. For example, a glue or other bond-inducing chemical means canbe used. Additionally, a variety of connections, such as threads, screwsor welds provide another means of attachment.

The disclosed method of manufacturing a sand control screen provides anumber of advantages over current manufacturing methods for sandscreens. The most critical step in the production of the present sandcontrol screen is micro-perforating the sheet metal. This step can beperformed under controlled conditions to produce reliable opening sizesand shapes with close tolerances in the spacing. The later steps ofshaping the sheet metal and attaching the shaped filter layer to thebase pipe can be performed in less controlled conditions withoutadversely affecting the quality of the sand control screen. Finalassembly can be performed closer to the point of use, such as at thewell site. Overhead can also be reduced by stocking only themicro-perforated sheet metal and assembling the sand control screens onuser-provided base pipe. Specific configurations of micro-perforationscan be produced quickly and shipped to the site to provide a custom-madefilter that more closely meets the need of the user's than the stocksizes currently available.

The disclosed sand control screen having a micro-perforated filter layeralso provides additional advantages over existing sand control screens.The use of a micro-perforated filter layer can result in a sand controlscreen having a reduced outside diameter for a given base pipe size. Thedecreased outside diameter and strong attachment can make installationeasier and may allow an increased base pipe size for a given holediameter. Additionally, the attachment of the filter layer and base pipealong the entire length of the filter layer provides a strong attachmentwith a lower incidence of detachment. Manufacturing costs are decreased,while the quality and durability of the filter are increased.

While this invention has been described with a reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is, therefore, intended that the appended claimsencompass any such modifications or embodiments.

1. A sand control screen comprising: a base pipe having at least oneopening that allows fluid flow therethrough; a filter layer attached tothe base pipe, the filter layer having a plurality ofmicro-perforations; and a drainage layer formed between the base pipeand the filter layer to allow fluid flow between the base pipe and thefilter layer.
 2. The sand control screen as recited in claim 1 whereinthe filter layer has a thickness between about 1/32nd of an inch andabout ¼th of an inch.
 3. The sand control screen as recited in claim 1wherein the filter layer is a sheet metal filter layer.
 4. The sandcontrol screen as recited in claim 1 wherein the shape of themicro-perforations at the surface of the filter layer is chosen from thegroup consisting of a circle, an ellipse and a slot.
 5. The sand controlscreen as recited in claim 1 wherein the shape of the micro-perforationsat the surface of the filter layer is chosen from the group consistingof a square, a triangle and a multi-sided polygon.
 6. The sand controlscreen as recited in claim 1 wherein the micro-perforations have amaximum width of 500 microns.
 7. The sand control screen as recited inclaim 1 wherein the micro-perforations have a tapering cross-sectionthrough the filter layer.
 8. The sand control screen as recited in claim1 wherein the filter layer is attached to the base pipe by one ofadhesion, a friction fit and fusion bonding.
 9. The sand control screenas recited in claim 1 wherein the drainage layer further compriseschannels.
 10. The sand control screen as recited in claim 9 wherein thechannels are formed in one of the outside surface of the base pipe andthe inside surface of the filter layer.
 11. The sand control screen asrecited in claim 1 wherein the drainage layer further comprises one ofwire wrap and wire mesh.
 12. A sand control screen comprising: a basepipe having at least one opening that allows fluid flow therethrough; asheet metal filter layer wrapped around the base pipe, the filter layerhaving a plurality of micro-perforations, the filter layer beingcorrugated to form channels between the filter layer and the base pipe;and at least one connector coupling the filter layer to the base pipe.13. The sand control screen as recited in claim 12 wherein the filterlayer has a thickness between about 1/32nd of an inch and about ¼th ofan inch.
 14. The sand control screen as recited in claim 12 wherein theshape of the micro-perforations at the surface of the filter layer ischosen from the group consisting of a circle, an ellipse and a slot. 15.The sand control screen as recited in claim 12 wherein the shape of themicro-perforations at the surface of the filter layer is chosen from thegroup consisting of a square, a triangle and a multi-sided polygon. 16.The sand control screen as recited in claim 12 wherein themicro-perforations have a maximum width of 500 microns.
 17. The sandcontrol screen as recited in claim 12 wherein the micro-perforations areplaced at the peaks and valleys of the corrugations.
 18. The sandcontrol screen as recited in claim 12 wherein the micro-perforations arespaced uniformly across the filter layer.
 19. A method of making a sandcontrol screen, the method comprising: fabricating a plurality ofopenings in the wall of a base pipe, the plurality of openings allowingfluid flow therethrough; creating a plurality of micro-perforations in alength of sheet metal having a first and a second edge opposite eachother to form a filter layer; forming a plurality of channels that allowfluid flow between the filter layer and the base pipe; shaping thefilter layer to fit around the base pipe wherein the first edge and thesecond edge of the filter layer are substantially adjacent each other;attaching the filter layer to the outer surface of the base pipe; andsealing the first edge of the filter layer to the second edge.
 20. Themethod of making a sand control screen as recited in claim 19, whereinthe filter layer is corrugated prior to the shaping step.
 21. The methodof making a sand control screen as recited in claim 19, wherein theshaping step and the attaching step are performed at the location wherethe sand screen is used.
 22. The method of making a sand control screenas recited in claim 19, wherein the attaching step uses an attachmentmethod chosen from the group of fusion bonding, friction fitting andadhesion.
 23. The method of making a sand control screen as recited inclaim 19, wherein the creating step creates micro-perforations having atapering cross-section.
 24. The method of making a sand control screenas recited in claim 23, wherein the shaping step orients a smalleropening of the tapering cross-section on the exterior of the filterlayer.
 25. The method of making a sand control screen as recited inclaim 19, wherein the creating step uses one of a water jet and a laserto create the micro-perforations.